Wheel-balancing method and device

ABSTRACT

The invention concerns a device for balancing a wheel comprising a rim and a tire. This device comprises a unit for measuring the wheel imbalance and a unit for scanning the rim dimensions. The scanner unit and the imbalance-measuring unit are connected to a computer which determines a rim contour from the scanner unit output signals and then the optimum positions and dimensions for the balance weights from the contour determined in conjunction with values supplied by the imbalance-measuring unit.

BACKGROUND OF THE INVENTION

The invention concerns a method and a device for balancing a wheel.

In prior devices and methods for the balancing of automobile wheels, thenominal data of the wheel rim are computed as wheel specific data or areevaluated by means of a measuring device. A computer provided in thebalancing device evaluates, thereafter, the positions and values of thebalancing weights.

The nominal data, however, in many cases do not correspond to thepositions in which the balancing weights may be mounted. Therefore, thebalancing positions have to be evaluated through correction factorswhich, however, constitute only mean values for various rim types andsizes. By using such average values, differences originate between thecalculated and the actual balancing positions which can lead to aninsufficient result in balancing.

A method for compensating the lack of balance on a automobile wheel isknown from the European patent application EPO 586 856 Al in which apick-up device is provided in order to manually pick up or determine,respectively, the positions on the outline of the rim at which thebalancing weights should be mounted according to the experience of theuser. In doing so, the pick-up is brought to the so-called balancingplanes where the balancing weights should be mounted later on. Thedeficiency of this known method is that the user decides during thepicking-up in which areas the balancing weights should be arranged.Furthermore, the known method is only applicable with standardized wheelshapes (standard wheels, flat-base rims, steep shoulder wheels etc.)which may be characterized by means of a few pick-up values on thevarious balancing planes.

SUMMARY OF THE INVENTION

It is the object of the invention to evaluate the optimal balancingvalues, as weight and positions for the balancing weights for any wheelforms without a user having to determine the balancing planesbeforehand.

This object is met by a method for balancing a wheel by means ofbalancing weights, wherein the dimensions of the wheel rim are scannedand the scanning values are fed to a computer which evaluates theoutline of the wheel from such scanning values, and wherein the optimalbalancing values are determined from the evaluated outline in connectionwith a measurement of the level or degree to which the wheel isunbalanced.

In a preferred embodiment of the method according to the invention, theevaluated outline as well as the optimal balancing values as determinedby the computer, in particular positions and values of the balancingweights, are graphically displayed on a display device at thecorresponding positions of the outline.

In a further preferred embodiment of the method according to theinvention, the balancing positions shown on the outline may be manuallymoved by a user through an input console, and these movements are takeninto account as boundary conditions in calculating the balancing valuesby the computer.

In a further preferred embodiment of the method according to theinvention, the scanning of the wheel comprises a picture detection inwhich pictures are converted into electrical signals, such that visibleportion of the rim is displayed as a picture in the picture scanningunit. The resulting scanned picture is fed to the computer whichevaluates the outline from the picture of the visible part of the rim.

In a further preferred embodiment of the method according to theinvention, the scanning of the wheel is effected by measuring thedistance between a distance meter and addressed points on the outline ofthe wheel rim.

The above object is furthermore met by a device for balancing a wheel bymeans of balancing weights comprising an unbalance measuring unit formeasuring the degree to which the wheel is unbalanced, a scanning devicefor scanning the wheel rim, and a computer being connected to thescanning device and the unbalance measuring device, wherein the scanningdevice is adapted to detect the outline of the wheel rim, and whereinthe computer is constructed such that the outline of the wheel may beevaluated from the output signals of the scanning device, and theoptimal balancing values for the balancing weights may be determinedfrom the evaluated outline in connection with the measuring values ofthe unbalance measuring device.

In a preferred embodiment of the device according to the invention, adisplay device is provided which is connected to the computer anddisplays the evaluated outline as well as the optimal balancing valuesat the corresponding positions of the outline graphically as determinedby the computer.

In a further preferred embodiment of the device according to theinvention, the scanning device comprises a pick-up which is guidedmanually across the wheel rim, and detectors are provided for detectingthe special movement of the pick-up, the output signals of the detectorsbeing received by the computer.

In another preferred embodiment of the device according to theinvention, the scanning device comprises a pick-up which is movable bymotor drives,

In another preferred embodiment of the device according to theinvention, the scanning device comprises a pick-up having a distancemeter which measures the distance between the pick-up and an addressedpoint of the outline of the wheel rim.

In another preferred embodiment of the device according to theinvention, the distance meter is pivotally arranged, and detectors areprovided for detecting the pivotal movement of the distance meter, theoutput signals of the detectors being received by the computer.

In an even further preferred embodiment of the device according to theinvention, the computer comprises a control unit for controlling themovement of the pick-up.

In another preferred embodiment of the device according to theinvention, the scanning device comprises a picture detecting unit.

In another preferred embodiment of the device according to theinvention, the picture detecting unit comprises a camera which detectsthe inner outline of the wheel, wherein the output signals of the cameraare usable by the computer for evaluating the outline.

Since the outline of the wheel is always known to the computer in alldetails by means of the scanned values, special situations can also betaken into account. For example, with adhesive weights, the computer mayadvantageously take into account the following criteria in optimizingthe positions for the balancing weights: The distance between the innerand outer balancing weights should be as large as possible in order tominimize the value of the weights and to put up the quality of thebalancing in connection with the material usage, the accuracy of thebalancing and the optical impression. Furthermore, it should be possibleto mount the weights by avoiding edges, corners, ribs, detents and thelike.

In the case of driven-in weights, the computer may advantageouslyanalyse the rim flange belonging to the outline of the rim and maydetermine, therefrom, the exact position for the driven-in weights.

Advantageously, a display device is connected to the computer on whichthe evaluated outline, as well as also the optimal positions of thebalancing weights at the corresponding locations of the outline asdetermined by the computer, are displayed in a graphical manner. Bymeans of this display, the optimal positions for mounting the balancingweights at the wheel may again be found. In case the optimal positionsas evaluated by the computer do not correspond to the desire of the useranyhow, e.g. in respect to the aesthetic impression, the balancingpositions displayed at the outline may advantageously be moved by handby the user through an input console. Thereafter, the computer againcomputes the required balancing values taking into account such boundaryconditions.

The scanning is made advantageously automatically by means of a guidedpick-up, e.g. a pick-up moved by a motor. However, even in a simpleembodiment of the invention where the manual guiding of a pick-up isprovided, the pick-up may be moved "blind" along the rim by a user Inany case, it is not necessary to bend down when looking into the wheelfor determining the balancing planes.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention is described by means of preferredembodiments with reference to the attached drawings, in which:

FIG. 1 shows a first embodiment of a device according to the invention;

FIG. 2 shows a second embodiment of the invention;

FIG. 3 shows a third embodiment of the invention;

FIG. 4 shows a fourth embodiment of the invention; and

FIG. 5 shows an example of an optimal positioning of the balancingweights according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A rim 1 is shown in cross section in FIG. 1 on which a tire 2 ismounted. The rim 1 with the tire 2 is rotatably mounted on a shaft 8. Apick-up device comprises a pick-up 3 which may by moved by means of adrive 4 in the horizontal direction (i.e. in parallel to the shaft 8)and by means of a drive 5 in the vertical direction (i.e. perpendicularto the shaft). The pick-up device 3 is connected to a computer (notshown).

In operation, the pick-up 3 is moved along the inner outline 15 of therim 1 by means of the two motor drives 4 and 5, wherein the horizontaland vertical positions of the pick-up are detected either through thedrives (e.g. stepping motors) themselves or by appropriate sensors (notshown). The output signals of the pick-up device are transferred to thecomputer which evaluates the inner outline of the rim in all points fromthe complete set of the signals. In a simple embodiment, wherein thedrives 4 and 5 are omitted, the pick-up is guided manually and along theoutline of the rim, and the horizontal and vertical positions of thepick-up are detected by sensors.

A second embodiment is shown in FIG. 2 which differs from the precedingembodiment in that the pick-up device comprises a distance meter 6 whichis manually movable or by means of the drive 4 in the horizontaldirection, the distance between the distance meter 6 and the respectivepoint addressed at the outline of the rim being detected. The computerthen evaluates from this measurement the complete outline of the rim ofthe wheel and takes this into account when calculating the balancingvalues.

In the embodiment of FIG. 3, the distance meter 6 is pivotally mountedwherein the movements in the horizontal and vertical directions arereplaced by a pivoting movement by means of an appropriate pivotingdrive 9. Also in this case, the distance between the distance meter 6and the respective point addressed at the outline of the rim isdetected, and the computer then evaluates from this measurement thecomplete outline of the rim of the wheel and takes this into account inthe calculation of the balancing values.

The distance meter 6 for measuring the distance to the respective pointaddressed at the outline of the rim may be a mechanical, optical,ultrasonic or electrical (inductive or capacitive) distance meter.

In FIG. 4, instead of the distance meter 6, a camera 10 is providedwhose picture scanning area 11 is chosen such that the inner outline ofthe rim may by scanned completely. The camera should, therefore, not bemoved back and forth or pivoted. The camera converts the receivedpicture into electrical signals which are processed in the connectedcomputer in such a way that the outline is evaluated from the picture ofthe scanned portion of the rim.

An example for the mounting of hidden adhesive weights is shown in FIG.5, the optimal positions 12 and 13 of which weights having beendetermined according to the invention.

In all embodiments a display device (not shown) may be provided which isconnected to the computer and graphically shows the evaluated outline aswell as the optimal balancing values at the corresponding positions ofthe outline as determined by the computer such that, by means of thedisplay, the optimal positions for mounting the balancing weights at therim of the wheel may be found.

What is claimed is:
 1. A method for balancing a wheel by means ofbalancing weights, comprising the steps of:measuring a degree the wheelis unbalanced; scanning the dimensions of the wheel rim and computingthe outline of the wheel rim from said scanning values; determiningoptimal balancing positions of the balancing weights on the wheel rimfrom the computed outline of the wheel rim; and computing the values ofthe balancing weights for balancing the wheel on the basis of saidoptimal balancing positions and the degree the wheel is unbalanced. 2.The method according to claim 1, further comprising the steps ofgraphically displaying the computed outline of the wheel rim, thecomputed optimal balancing positions of the balancing weights on thewheel in conjunction with the rim, and values of the balancing weightsat said optimal balancing positions of the outline of the wheel rim. 3.The method according to claim 2, wherein said step of computing theoptimal balancing positions includes variably selecting balancingpositions relative to the outline of the wheel rim on the display, andcalculating the values of the balancing weights based on using theselected balancing positions and the degree the wheel is unbalanced. 4.The method according to claim 1, wherein the step of scanning the wheelrim comprises scanning a visible portion of the rim and computing theoutline from the picture of the visible portion of the rim.
 5. Themethod according to claim 1, wherein the step of scanning the wheel rimincludes measuring a distance between a distance meter and addressedpoints on the outline of the wheel rim.
 6. A device for balancing awheel by means of balancing weights comprising:an unbalance measuringunit for measuring the degree that the wheel is unbalanced; a scanningdevice for scanning the wheel rim, and a computer being connected to thescanning device and the unbalance measuring device, wherein the scanningdevice includes means for detecting an outline of the wheel rim, and thecomputer includesmeans for evaluating the outline of the wheel from theoutput signals of the scanning device, means for determining optimalbalancing positions of the balancing weights on the wheel rim; and meansfor computing the values of the balancing weights for balancing thewheel on the basis of said optimal balancing positions and the degreethe wheel is unbalanced.
 7. The device according to claim 6, furthercomprising a display device connected to the computer for displaying theevaluated outline of the wheel rim, the computed optimal balancingpositions of the balancing weights on the wheel rim and the values ofthe balancing weights at said optimal balancing positions of the outlineof the wheel rim.
 8. The device according to claim 6, wherein thescanning device includes a pick-up which is guided manually across thewheel rim, and detectors for detecting the movement of the pick-up, theoutput signals of the detectors being received by the computer.
 9. Thedevice according to claim 6, wherein the scanning device comprises apick-up which is movable by motor drives.
 10. The device according toclaim 8, wherein the scanning device comprises a pick-up having adistance meter which measures the distance between said pick-up and anaddressed point of the outline of the wheel rim.
 11. The deviceaccording to claim 10, wherein the distance meter is pivotally arranged,and detectors are provided for detecting the pivotal movement of thedistance meter, the output signals of the detectors being received bythe computer.
 12. The device according to claim 9, wherein the scanningdevice comprises a pick-up having a distance meter which measures thedistance between the pick-up and an addressed point of the outline ofthe wheel rim.
 13. The device according to claim 12, wherein thedistance meter is pivotally arranged, and detectors are provided fordetecting the pivotal movement of the distance meter, the output signalsof the detectors being received by the computer.
 14. The deviceaccording to claim 9, wherein the computer includes means forcontrolling the movement of the pick-up.
 15. The device according toclaim 6, wherein the scanning device includes a picture detecting unit.16. The device according to claim 15, wherein the picture detecting unitincludes a camera which detects the inner outline of the wheel, theoutput of the signals are outputted to the computer for evaluating theoutline.
 17. A device for balancing a wheel by means of balancingweights comprising:an unbalance measuring unit for measuring the degreethat the wheel is unbalanced; a scanning device for scanning the wheelrim, and a computer being connected to the scanning device and theunbalance measuring device, wherein the scanning device includes apick-up which is guided manually across the wheel rim, and detectors fordetecting the movement of the pick-up, the output signals of thedetectors being received by the computer, and the computer includesmeansfor determining optimal balancing positions of the balancing weights onthe wheel rim; and means for computing the values of the balancingweights for balancing the wheel on the basis of said optimal balancingpositions and the degree the wheel is unbalanced.
 18. A device forbalancing a wheel by means of balancing weights comprising:an unbalancemeasuring unit for measuring the degree that the wheel is unbalanced; ascanning device for scanning the wheel rim, and a computer beingconnected to the scanning device and the unbalance measuring device,wherein the scanning device includes a pick-up which is movable by motordrives, and the computer includesmeans for evaluating the outline of thewheel from the output signals of the scanning device, means fordetermining optimal balancing positions of the balancing weights on thewheel rim; and means for computing the values of the balancing weightsfor balancing the wheel on the basis of said optimal balancing positionsand the decree the wheel is unbalanced.
 19. A device for balancing awheel by means of balancing weights comprising:an unbalance measuringunit for measuring the degree that the wheel is unbalanced; a scanningdevice for scanning the wheel rim, and a computer being connected to thescanning device and the unbalance measuring device, wherein the scanningdevice includes a picture detecting unit, and the computer includesmeansfor evaluating the outline of the wheel from the output signals of thescanning device, means for determining optimal balancing positions ofthe balancing weights on the wheel rim; and means for computing thevalues of the balancing weights for balancing the wheel on the basis ofsaid optimal balancing positions and the degree the wheel is unbalanced.